Snap action type inertia switch with vibration amplication and actuator means

ABSTRACT

A device for detecting vibration of a surface on which the device is mounted includes a pair of levers mounted so that movement of one of them about a first pivot causes amplified movement of the other about a second pivot. The first lever is pivoted at one end about the first pivot and integral with a mass that tends to remain stationary, because of its inertia, when the surface vibrates. The end of that lever opposite its pivot engages the second lever at a point relatively close to the second pivot. The end of the second lever opposite the second pivot is highly sensitive to vibration in that it moves a considerable distance in response to a small relative movement of the surface with respect to the mass. The free end of the second lever normally holds an alarm-actuating mechanism in a cocked condition but releases it, so that a single-pole, double-throw switch is operated and an alarm is given, in response to vibration exceeding a predetermined intensity. The alarmactuating mechanism is released also in response to separation of the device from the surface. The device is useful in burglary detection, for example in detecting breakage of glass (the device can replace the foil often used for this purpose) and in detecting attempts to burglarize steel or concrete vaults and other enclosures made of relatively strong, rigid materials.

limited States Patent [191 Hall [ SNAP ACTION TYPE INERTIA SWITCH WITH VIBRATION AMPLICATION AND ACTUATOR MEANS [75] Inventor: Robert A. Hall, Montclair, NJ.

[73] Assignee: Guardian Industries, Inc.,

Springfield, NJ.

22 Filed: Sept. 29, 1972 21 Appl. No.: 293,354

[52] US. Cl ZOO/61.45 R, 73/71, 200/615 [51] Int. Cl. I-I01h 35/14 [58] Field of Search 200/6 B, 61.45 R, 61.5,

ZOO/61.51; 340/261, 262, 266; 73/71, 490, 514, 517 R, 517 AV Primary ExaminerJames R. Scott Attorney, Agent, or FirmBrumbaugh, Graves,

Donohue & Raymond [451 Jan. 21, 1975 [57] ABSTRACT A device for detecting vibration of a surface on which the device is mounted includes a pair of levers mounted so that movement of one of them about a first pivot causes amplified movement of the other about a second pivot. The first lever is pivoted at one end about the first pivot and integral with a mass that tends to remain stationary, because of its inertia, when the surface vibrates. The end of that lever opposite its pivot engages the second lever at a point relatively close to the second pivot. The end of the second lever opposite the second pivot is highly sensitive to vibration in that it moves a considerable distance in response to a small relative movement of the surface with respect to the mass. The free end of the second lever normally holds an alarm-actuating mechanism in a cocked condition but releases it, so that a singlepole, double-throw switch is operated and an alarm is given, in response to vibration exceeding a predetermined intensity. The alarm-actuating mechanism is released also in response to separation of the device from the surface. The device is useful in burglary detection, for example in detecting breakage of glass (the device can replace the foil often used for this purpose) and in detecting attempts to burglarize steel or concrete vaults and other enclosures made of relatively strong, rigid materials.

6 Claims, 4 Drawing Figures I8 g? i 45 mi 90 Patented Jan. 21, 1975 2 Sheets-Sheet 2 FIG. 4

SNAP ACTION TYPE INERTIA SWITCH WITH VIBRATION AMPLICATION AND ACTUATOR MEANS BACKGROUND OF THE INVENTION This invention relates to vibration detectors and, more particularly, to a novel and highly-effective twinbeam vibration detector for protection against burglaries.

Vibration detectors, including detectors for protection against burglaries, are known. A typical conventional detector comprises a protective circuit kept closed by a blade spring that holds two contacts together. One contact is mounted on the blade, and the other is fixed to the housing. The force F, with which the two contacts are pressed together can be adjusted by means of a set screw that pushes against the blade. A mass is attached to the blade near the point where the contact is attached. When the housing experiences an acceleration, the mass tends to stay behind because of inertia. If the inertial force is greater than the spring force F,,, then the contacts will open, breaking the protective circuit and initiating an alarm.

Such a detector has serious deficiencies. For example:

1. Its ability to discriminate between low-frequency background noise and sharp impacts is limited.

2. The force F between the contacts determines the sensitivity of the device; i.e., the sensitivity of the detector can be increased only by reducing the contact force F,,, which increases the risk of false alarms.

3. After a detector initiates an alarm it returns to its original state. This is a serious problem when there are several detectors in series in the same circuit. If one of them is causing false alarms because it is too sensitive, there is no easy way to determine which one it is.

Another detector is disclosed in my U.S. Pat. No. 3,392,246, issued July 9, 1968, for Vibration Detection Device. This detector is significantly better than the one described above in that it provides separate actuating means for positively opening the contacts and keeping them open in, response to vibration exceeding a predetermined intensity. This patented detector overcomes the three deficiencies of earlier detectors set forth above and is regarded as the best detector for protection against burglary up to the time of the present invention.

SUMMARY OF THE INVENTION An object ofthe invention is to advance further the art of vibration detection, especially as it applies to burglary protection. In particular, an object of the invention is to provide a vibration detector that'avoids the problems outlined above and that moreover has increased sensitivity and is more difficult to circumvent.

The foregoing and other objects are attained in accordance with the invention by the provision of a detector for mounting on a surface to detect vibration of the surface, comprising a mass, mounting means for mounting the mass movably with respect to the surface so that the mass can remain relatively stationary when the surface virates, and amplifying means responsive to the relative movement of the mass with respect to the surface for effecting an amplification of .the relative movement. Indicator means preferably comprising a visible flag and an alarm such as a bell and responsive to the amplification indicates when vibration of the surface or shock to the detector exceeding a predetermined intensity has occurred.

The mounting -means preferably comprises a first pivot and a first lever pivoted about the first pivot and integral with the mass, and the amplifying means preferably comprises a second pivot and a second lever pivoted about the second pivot. The first lever engages the second lever, at a point relatively close to the second pivot, in such a manner that movement of the first lever about the first pivot causes movement of the second lever about the second pivot. The indicator responds to movement of a portion of the second lever relatively far from the second pivot.

The detector includes also a plunger movable between first and second positions and permitting, in the first position, latching of the detector in the cocked condition and preventing, in the second position, latching of the detector in the cocked condition. Biasing means biases the plunger towards the second position, and the plunger is forced to the first position when the detector is mounted on the surface, so that the detector can be latched in the cocked condition in the absence of vibration exceeding the predetermined intensity when the detector is mounted on the surface but cannot be latched in the cocked condition, and hence assumes the actuated condition, when the detector is removed from the surface and the biasing means moves the plunger to the second position.

The detector comprises a single-pole, double-throw switch for initiating the alarm. Three contacts are respectively electrically connected to three terminals,

- one of the contacts being normally closed with respect to a second and open with respect to the third of the contacts. The mass and associated structure serve as actuating means responsive to vibration of the surface exceeding a predetermined intensity for opening the first contact with respect to the second and closing the first contact with respect to the third. This provides alternate ways of initiating the alarm and makes the device more difficult to circumvent.

BRIEF DESCRIPTION OF THE DRAWING An understanding of other aspects of the invention can be gained from a consideration of the following detailed description of the preferred embodiments thereof, in conjunction with the appended figures of the drawings, wherein:

FIG. 1 is a broken-away perspective view showing apparatus in accordance with the invention in a cocked condition;

FIG. 2 is a view similar to FIG. 1 showing the apparatus in an actuated condition;

FIG. 3 is a sectional view of the apparatus in elevation; and

FIG. 4 is a schematic diagram showing the electrical part of the apparatus in the cocked condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS space to be made secure against burglary. The detector is designed to respond to high-frequency vibration of the surface 12, such as vibration characteristically produced by a hammer striking the surface, but not to low-frequency vibration, such as that characteristically produced by wind or traffic.

A substantial mass 14 is movably mounted with respect to the surface 12 so that the mass can remain relatively stationary, because of its inertia, when the surface 12 vibrates. The mounting means for the mass 14 comprises, in the preferred embodiment, a first beam or lever 16 pivoted at one end about a first pivot 18. The pivot 18 is stationary with respect to the surface 12, and the mass 14 is integral with the lever 16. A compression spring 19 pushes the other end 20 of the first lever 16 against a second lever 22 with a force that can be adjusted by turning a set screw 19. The end 20 of the lever 16 actuates a mechanical amplifier comprising a second beam of lever 22 of low mass pivoted about a second lever 24. The pivot 24 is also stationary with respect to the surface 12. The point of engagement of the lever 16 with the lever 22 is at an arm 23 integral with the lever 22 and relatively close to the pivot 24. Movement of the first lever 16 about the first pivot 18 thus causes movement of the second lever 22 about the second pivot 24.

The end 26 of the second lever 22 opposite the second pivot 24 is relatively far from the pivot 24 as compared to the distance between the arm 23 and the pivot 24 and thus highly sensitive to vibration in that it moves a considerable distance in response to a small relative movement of the surface 12 with respect to the mass 14. Advantage is taken of this feature to actuate an indicator, which may comprise a visible flag and an audible alarm and which indicates when vibration of the surface 12 exceeding a predetermined intensity has occurred. The second lever 22 is formed at its end 26 with latch means comprising a notch 28 that engages .a tab 30 integral with a member 32 from which another tab 34 is upstanding. A link 36 has an eye 38 that fits over the tab 34 and a tab 40 that fits through a slot 42 in a phosphor-bronze blade 44 that acts as the common contact of a single-pole, double-throw switch.

When the member 32 is in the position illustrated in FIG. 1, the link 36 forces the blade 44, which is resilient, to the postion shown in FIG. 1; when the notch 28 is disengaged from the tab 30, the blade 44 snaps clockwise (from the perspective of the figures) to the position of FIG. 2, rotating the member 32 90 clockwise in a slot 48 and bearing 48 formed in a dust cover 50.

The member 32 includes indicator means such as a flag 46 extending through the slot 48 to provide an external visible indication of the condition of the detector (cocked or actuated). This is an important feature when there are several detectors in series in the same circuit. If one of them is causing the false alarms because it is adjusted to be too sensitive, it is easy to determine which one it is. The flag 46 also facilitates cocking the detector after its actuation. It is simply engaged manually and pushed counterclockwise.

The second lever 22 is biased in a clockwise direction from the perspective of the figures by a tension coil spring 52 so that the notch 28 engages the tab 30 in the cocked condition (FIG. I) and safely holds the detector in that condition until the device is actuated.

When the device is cocked (FIG. 1), the blade 44 does not push on the link 36 in a direction parallel to the lever 22 (perpendicular to the outer vertical wall defining the notch 28) but rather pushes down towards, but slightly to the right of, the axis of rotation of the member 32. The frictional force between the outer vertical wall defining the notch 28 and the outer vertical wall of the tab 30 when the device is cocked (FIG. 1) is thus low, even though the spring 44 pushes rather hard on the link 36. This makes for a highly sensitive device, easy to actuate, and one which, when actuated, operates reliably. Normally, the set screw 19 is adjusted so that the counterclockwise force exerted on the lever 22 by the spring 19 acting through the lever 16 is almost enough to overcome the clockwise force of the spring 52. Then a small additional torque provided by the inertial force on the mass 14 when the detector is accelerated is sufficient to actuate the device. When the mass 14 moves with respect to the surface 12 by a very small distance, which may be less than onethousandth of an inch, this movement is amplified by the lever 22 so that the tab 30 is freed and the blade 44 moves the member 32 to the position of FIG. 2. When vibration or shock exceeding a predetermined intensity occurs, the lever 22 momentarily moves counterclockwise, but not beyond the point where the lever 16 engages another arm 23' integral with the lever 22 and on the side of the pivot 24 opposite the arm 23. The device then snaps to the actuated condition (FIG. 2), initiating an alarm.

Th alarm is also actuated if the detector 10 is removed from the surface, even in the absence of vibration. To this end, a plunger is provided at the free end of a lever 72 pivoted about a pivot 74. The lever 72 carries an arm 76 that is slightly spaced apart from the lever 22 when the detector is mounted on the protected surface 12 and cocked. The lever 72 is biased in a counterclockwise direction from the perspective of the figures by a compression coil spring 78. So long as the detector is mounted on the protected surface 12, the plunger 70 is depressed to a first position, shown in FIG. 1 and shown in solid outline in FIG. 3, by the sur face 12, and the detector can be cocked by counterclockwise rotation of the flag 46. If, however, the detector becomes detached from the surface 12, whether because of failure of its means of attachment or because of the deliberate action of a burglar in preparation for an attack on the surface, the spring 78 forces the lever 72 counterclockwise, the plunger 70 moves to a second position shown in FIG. 2 and in dot-dash outline in FIG. 3, and the arm 76 engages the lever 22 and moves it counterclockwise so that the notch 28 becomes disengaged from the tab 30. This causes immediate actuation of the device in the manner previously described. The device is thus hard to circumvent by mechanical measures.

The new detector of double-beam construction can be adjusted from an insensitive setting to a setting ten to a hundred times more sensitive to shocks than prior single-beam detectors and is therefore better adapted to protect steel or concrete vaults and other enclosures made of relatively strong, rigid materials. Moreover, it discriminates better between low-frequency and highfrequency vibrations. It is thus less prone to false alarms due to background noise. In addition, it has the advantages, characteristic of the best prior detectors, of a contact pressure independent of the sensitivity setting, of locking in the alarm position so that the response time of the control unit has no effect on the operation of the alarm, and of a flag visible from the outside making it easy to determine which detector ofa series of detectors has caused the alarm.

FIG. 4 shows the electrical part of the apparatus. The blade 44 is the movable element of a single-pole, double-throw switch 45 and is formed with a first contact 84 which, when the detector is cocked, is closed with respect to a second contact 86 and open with respect to a third contact 88. The contact 84 is electrically connected to a first terminal 90, the contact 86 is electrically connected to a second terminal 92, and the contact 88 is electrically connected to a third terminal 94 (FIGS, 1 and 2).

A battery 100 has its positive terminal 102 connected through a resistance 104 to the normally closed contact 86. The positive terminal 102 and the negative termial N6 of the battery 100 are connected by lines 108 and lit) to opposite ends of the coil 112 of a relay. So long as current flows through the coil, a blade switch lll4l controlled by the relay is maintained in the open position against the tension of biasing means such as a spring 116.

If the contacts 86 and 84 are separated, the current through the coil 112 is interrupted, and the blade switch 114 closes with the contact 118. This completes a circuit from a battery 1120 to an alarm 122 such as a bell. If the contacts 86 and 84 are shunted, current through the coil 112 is nevertheless interrupted when the contacts 84 and 88 are closed, since this shorts the battery 180 and also shorts the coil 112.

The described structure is important in burglary detection, since it makes the detector hard to circumvent by electrical measures. Placing a shunt across the detector does not circumvent it (the alarm will still be actuated when the surface vibrates and the contacts 84 and 88 are closed); moreover, an attempt to circumvent the device by means of a shunt actuates the alarm at once if the shunt is applied by mistake between the lines 108 and lit); in addition, cutting the circuit actuates the alarm.

A number of devices 10 can be inserted in the same house lines 108, lllltl so that a number of doors, windows, etc., of a single building or apartment can be protected by the same system, as indicated by additional units lltl, Ml" in phantom outline.

Thus there is provided in accordance with the invention a novel and highly-effective detector having particular utility in burglary protection. It is very sensitive to vibration characteristic of an attempted burglary and difficult to circumvent by mechanical or electrical measures. Many modifications of the preferred embodiment described above will readily occur to those skilled in the art upon consideration of this disclosure. For example, the mounting of the mass 14 and the amplification of the movement of the mass with respect to the surface can be effected by structure other than levers. Moreover, if levers are used, they need not be pivoted at their ends, the portion of the lever 16 that engages the lever 22 need not be at the end of the lever l6, and the portion of the lever 22 forming the latching notch 28 need not be at the end of the lever 22. Further, the indicator means can comprise, in addition to or in place of a bell, flashing lights, a taped message, etc., for the purpose of giving an alarm locally or at the nearest police station. Accordingly, the invention is to be construed as including all of the embodiments thereof within the scope of the appended claims.

I claim:

1. A detector for mounting on a surface to detect vibration of the surface, comprising: a mass, mounting means for mounting the mass movably with respect to the surface so that the mass can remain relatively stationary when the surface vibrates, mechanical amplifying means responsive to the relative movement of the mass with respect to the surface for amplifying the relative movement and producing a mechanicallyamplified output, and indicator means responsive to the mechanically-amplified output for indicating when vibration of the surface exceeding a predetermined intensity has occurred, wherein the mounting means comprises first pivot means and first lever means pivoted about the first pivot means and integral with the mass, wherein the mechanical amplifying means comprises second pivot means and second lever means pivoted about the second pivot means, the first lever means engaging the second lever means, at a point relatively close to the second pivot means, in such a manner that movement of the first lever means about the first pivot means causes movement of the second lever means about the second pivot means, and wherein the indicator means responds to movement of a portion of thesecond lever means relatively far from the second pivot means.

2. In a detector that can assume alternately a cocked condition and an actuated condition and that can be mounted on a surface to detect vibration of the surface when the surface or adjacent structure is attacked, an improvement that prevents circumvention of the detector by removing it from the surface before the attack and that comprises latch means for latching the detector in the cocked condition, actuating means for releasing the latch means in response to vibration of the surface exceeding a predetermined intensity, thus permitting the detector to assume the actuated condition, indicator means providingan indication in response to the assumption of the actuated condition, plunger means movable between first and second positions and permitting, in the first position, latching of the detector in the cocked condition by the latch means and preventing, in the second position, latching of the detector in the cocked condition, and biasing means biasing the plunger means towards the second position, the plumger means being forced to the first position when the detector is mounted on the surface, so that the detector can be latched in the cocked condition in the absence of vibration exceeding the predetermined intensity when the detector is mounted on the surface but cannot be latched in the cocked condition, and hence assumes the actuated condition, when the detector is removed from the .surface and the biasing means moves the plunger means to the second position.

3. In a detector for mounting on a surface to detect vibration of the surface, an improvement that prevents circumvention of the detector by electrically shunting it and that comprises relay means, a power supply, three terminal means, three contact means respectively electrically connected to the three terminal means, one of the contact means being normally closed with respect to a second and open with respect to the third of the contact means, thereby placing the relay means in circuit with the power supply, and means responsive to vibration of the surface exceeding a predetermined intensity for opening the first contact means with respect to the second and closing the first contact means with respect to the third, thereby shorting the relay means,

the means responsive to vibration of the surface comprising a relatively stationary mass mounted movably with respect to the surface so that the mass can remain relatively stationary when the surface vibrates.

4. A detector for mounting on a surface to detect vibration of the surface, comprising: a first lever, first pivot means mounting said first lever for pivotal movement, a second lever, second pivot means mounting said second lever for pivotal movement, and latch means engageable with said second lever at a point spaced apart from said second pivot for holding said detector in a cocked condition, said first lever engaging said second lever at a point relatively close to said second pivot as compared to the separation between said latch means and said second pivot, said first lever responding to vibration of said surface exceeding a pre determined intensity by pivoting about said first pivot and causing pivoting of greater amplitude by said sec ond lever about said second pivot, whereby said latch means is actuated to permit said detector to move in an actuated condition.

5. A detector according to claim 1 wherein the indicator means comprises a flag visible outside the detector and movable in response to the mechanicallyamplified output.

6. A detector according to claim 1 wherein the indicator means comprises an audible alarm and electrical switch means for actuating the alarm, the electrical switch means being actuated in response to the mechanically-amplified output.

33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,862,386 Dated January 21, 1975 Inv nwfl Robert A. Hall It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

r" I On the Cover Page, after [54] Title, "AMPLICATION" should read --AMPLIFICATION--; col. 1, line 64, "virates" should read --vibrates; col. 3, line 55, after "causing" delete "the"; col. 4, line 28, "Th" should read -'I'he--; col. 5, end of line 15, "termial" should read '-terminal-; and col. 8, line 4, "in" should read -to-.

Signed and sealed this 6th day of May l975.

(SEAL) Attest:

. C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks zgggg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,862,386 .Dated January 21, 1975 Invent fls) Robert A. Hall It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

4 On the Cover Page, after [54] Title, "AMPLICA'IION" should read -AMPLIFICATION; col. 1, line 64, "virates" should read -vibrates; col. 3, line 55, after "causing" delete "the"; col. 4, line 28, "Th" should read --The--; col. 5, end of line 15, "termial" should read 'terminal-; and col. 8, line 4, "in" should read -to-.

Signed and sealed this 6th day of May 1975.

(SEAL) Attest:

, C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. A detector for mounting on a surface to detect vibration of the surface, comprising: a mass, mounting means for mounting the mass movably with respect to the surface so that the mass can remain relatively stationary when the surface vibrates, mechanical amplifying means responsive to the relative movement of the mass with respect to the surface for amplifying the relative movement and producing a mechanically-amplified output, and indicator means responsive to the mechanically-amplified output for indicating when vibration of the surface exceeding a predetermined intensity has occurred, wherein the mounting means comprises first pivot means and first lever means pivoted about thE first pivot means and integral with the mass, wherein the mechanical amplifying means comprises second pivot means and second lever means pivoted about the second pivot means, the first lever means engaging the second lever means, at a point relatively close to the second pivot means, in such a manner that movement of the first lever means about the first pivot means causes movement of the second lever means about the second pivot means, and wherein the indicator means responds to movement of a portion of the second lever means relatively far from the second pivot means.
 2. In a detector that can assume alternately a cocked condition and an actuated condition and that can be mounted on a surface to detect vibration of the surface when the surface or adjacent structure is attacked, an improvement that prevents circumvention of the detector by removing it from the surface before the attack and that comprises latch means for latching the detector in the cocked condition, actuating means for releasing the latch means in response to vibration of the surface exceeding a predetermined intensity, thus permitting the detector to assume the actuated condition, indicator means providing an indication in response to the assumption of the actuated condition, plunger means movable between first and second positions and permitting, in the first position, latching of the detector in the cocked condition by the latch means and preventing, in the second position, latching of the detector in the cocked condition, and biasing means biasing the plunger means towards the second position, the plumger means being forced to the first position when the detector is mounted on the surface, so that the detector can be latched in the cocked condition in the absence of vibration exceeding the predetermined intensity when the detector is mounted on the surface but cannot be latched in the cocked condition, and hence assumes the actuated condition, when the detector is removed from the surface and the biasing means moves the plunger means to the second position.
 3. In a detector for mounting on a surface to detect vibration of the surface, an improvement that prevents circumvention of the detector by electrically shunting it and that comprises relay means, a power supply, three terminal means, three contact means respectively electrically connected to the three terminal means, one of the contact means being normally closed with respect to a second and open with respect to the third of the contact means, thereby placing the relay means in circuit with the power supply, and means responsive to vibration of the surface exceeding a predetermined intensity for opening the first contact means with respect to the second and closing the first contact means with respect to the third, thereby shorting the relay means, the means responsive to vibration of the surface comprising a relatively stationary mass mounted movably with respect to the surface so that the mass can remain relatively stationary when the surface vibrates.
 4. A detector for mounting on a surface to detect vibration of the surface, comprising: a first lever, first pivot means mounting said first lever for pivotal movement, a second lever, second pivot means mounting said second lever for pivotal movement, and latch means engageable with said second lever at a point spaced apart from said second pivot for holding said detector in a cocked condition, said first lever engaging said second lever at a point relatively close to said second pivot as compared to the separation between said latch means and said second pivot, said first lever responding to vibration of said surface exceeding a predetermined intensity by pivoting about said first pivot and causing pivoting of greater amplitude by said second lever about said second pivot, whereby said latch means is actuated to permit said detector to move in an actuated condition.
 5. A detector according to claim 1 wherein the indicator means comprises a flag visible outside the detEctor and movable in response to the mechanically-amplified output.
 6. A detector according to claim 1 wherein the indicator means comprises an audible alarm and electrical switch means for actuating the alarm, the electrical switch means being actuated in response to the mechanically-amplified output. 